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EvilSpike

First RC Build Terra Scorcher

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I wouldn't say that the Sport Tuned was a mistake as such - it is a reliable motor that gives a fair bit more performance than the standard silver can. However the chassis is capable of handling a fair bit more. The drivetrain wouldn't have any trouble with a 13.5t brushless setup for example, once you upgrade the "coathanger" propshaft.

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And also new bits have arrived...

IMG-20200603-WA0000

The Absima wheels are just cheap ones with onroad tyres, but the JC Racing Pepper Pots are going to look soooooo Ossum™.

The hex's turned up today and I've fitted them. I bought 5, 6 and 7mm width ones as I didn't know which I'd need and the postage for one set was more expensive than the alu parts themselves. Doing up the tiny alen head bolt as tight as possible didn't actually lead to them clamping onto the driveshaft, but once the wheel is in place it holds the hex and the locking pin captive.

I can't say the Absima wheels look any good whatsoever, but I'm hoping it'll drive far better on tarmac with them. I think it's raining tomorrow but I'm rather keen to see how it goes. When the local model shop opens whenever that may be I'll take the pepper pots in and get some good, suitable tyres for the astroturf/hardpack/gravel.

Thanks for the help and encouragement everyone :)

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It seems that every time I take the car out something ends up falling off or breaking. I'd understand if I was flinging it off jumps and down steps but it's mainly just zipping around which is a little frustrating.

Last week the car decided to start losing contact with the transmitter. As I'd not painted the inner tray you could see the Futuba radio receiver blinking it's LED light. It had been working perfectly fine for three weeks and it took stripping out all the electronics, re-pairing the system a couple of times and reinstalling everything before it began behaving properly.

Yesterday whilst moving house we took a little break and I took the car for a spin on the driveway. Suddenly there was the sound of plastic scraping across asphalt and the car was dragging it's nose on the floor. One of the front suspension units has failed. The piston rod has come unscrewed from the lower mount, and the yellow spring retainer and spring made a bid for freedom. They were easily found, but my tools are packed so I can't undo the lower mount and screw it back in easily. I'm hoping it's not stripped the yellow plastic thread out of the shock base but I won't know until I try.

I did have a look last night to try and find a set of aluminium shocks for it, but even though I know the part numbers of the sprues, I can't find the length of the shocks quoted anywhere.

Would anyone know what they are and have a suggestion of a decent set of shocks to buy please?

Thank you!

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Sorry to read of your bits-falling-off troubles. Seems you are having a run of bad luck. Usually this is a pretty reliable chassis. The only thing that has ever fallen off my Thundershot is a wheel nut!

As for the shocks, can you base your measurements off the ones currently fitted perhaps?

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Certainly sounds like bad luck! The only issue I've had with the original style CVA's is when i have had a heavy impact and the shock cap popped off.

Most common issue recently now I'm starting to jump and launch off inclines and bumps in the terrain is bent drive shafts after cartwheeling from a bad landing.......

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2 hours ago, TurnipJF said:

Sorry to read of your bits-falling-off troubles. Seems you are having a run of bad luck. Usually this is a pretty reliable chassis. The only thing that has ever fallen off my Thundershot is a wheel nut!

As for the shocks, can you base your measurements off the ones currently fitted perhaps?

I think much of it is my inexperience in how tight I ought to do up bolts, nuts and screws into the plastics. When working on motorbikes every part pretty much has a torque value ascribed to it in the manual which means I'm sure I'm doing it right. Here I'm a little lost!

When I've managed to dig the toolbox out of the garage I'll get the Vernier calipers onto the shocks, I'm guessing it's eye to eye length I need to measure? I did wonder if there was a go to set of shocks that everyone puts on this chassis family. I've no idea about which brands to search for or avoid as I'm so new to this game.

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7 hours ago, EvilSpike said:

When I've managed to dig the toolbox out of the garage I'll get the Vernier calipers onto the shocks, I'm guessing it's eye to eye length I need to measure?

Aye, 'tis eye to eye.

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8 hours ago, EvilSpike said:

I think much of it is my inexperience in how tight I ought to do up bolts, nuts and screws into the plastics. When working on motorbikes every part pretty much has a torque value ascribed to it in the manual which means I'm sure I'm doing it right. Here I'm a little lost!

When I've managed to dig the toolbox out of the garage I'll get the Vernier calipers onto the shocks, I'm guessing it's eye to eye length I need to measure? I did wonder if there was a go to set of shocks that everyone puts on this chassis family. I've no idea about which brands to search for or avoid as I'm so new to this game.

Upgrade shocks are tricky for these because the front shocks are so short (64mm eye to eye). Most modern buggy shocks are 75mm. That said, my Thunder Dragon (same chassis) ran really nicely with 60mm touring car shocks on the front with longer eyelets to get them to around 64mm long to fit. The shorter stroke and stiff springs suited the car. To be honest i have never had a tamiya ahock unscrew like that and alloy shocks will have the same plastic end arrangements to i would stick with trying to do them up a little tighter. A new sprue with replacement parts is only a few pounds so it3not super expensive to risk some more twist. Another thibg if you are particularly concerned is to dab a bit of household plastic glue on the threads as threadlock. Nothing strong like super glue, just  common household/craft glue you might stick the kids toys back together with. You want to be able to get the ends off again at some point, but a bit of something tacky will hold them tight. 

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Well it's been a while!

Anyway, after another hour or so of run time mainly on the asphalt of the road outside the house the next thing to come loose was the motor mount.  It was the two short bolts that hold the motor to the aluminium mount rather than the longer two which couple the mount to the gearbox. Neither of these I tread-locked first time around, not a mistake I have made now. And since I was opening it up I might as well fit the Sport Tuned motor I'd bought a long time ago.

2020-08-29 19.36.56

 

2020-08-29 20.46.27


I do find it a bit odd that Tamiya have an an almost entirely different colour system for the wires on both motors (green/yellow and red/black) compared to their ESC (yellow/blue). Is this a legacy thing or is Stevie Wonder moonlighting as an electronics guy?

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Well the new motor certainly gives it a bit more thrust. It's like someone's popped a bit of ginger up a racehorses bottom! Not sure how people manage to accurately control these things with lithium batteries and brushless motors, but I guess there's only one way to find out. But that'll be for another day.

Whilst I was away I bought some shock absorbers in 65/85mm lengths from t' bay o' ghey d'rekly from China. The supplier was surpriseonline022 and indeed it was a surprise. For £10 I got four shocks which actually measured 58/85mm in length. The bodies don't look too bad and are indeed spun on a lathe out of (the cheapest possible) alu.

2020-08-31 22.53.59

None of the shocks came filled with oil, the rear springs seem about right and the rear piston has two oil flow damping holes. The front springs are stupidly rock hard and yet the piston has no damping holes although the bore clearance is massive. To be honest I might actually fill up the rears with oil and see what they are like, but I want a set of four for obvious reasons. The front shocks aren't even worth considering really. I could cut down the spring to reduce the overstressed spring, but the incorrect length would have the car on its nose whilst still being over sprung and over damped. It'll oversteer everywhere!

2020-08-31 22.56.51

So yeah, that was a waste of a tenner...

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Thanks for posting your build thread. I found it as I too lost the same rear suspension bolt and associated parts! I bought the damper bushings linked in this thread, just need the rest now.

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On 8/31/2020 at 11:43 PM, EvilSpike said:

 Not sure how people manage to accurately control these things with lithium batteries and brushless motors, but I guess there's only one way to find out. But that'll be for another day.

While I have not run brushless in any of mine, I have run 11 turn motors and even 13T motors on 9.6v with top speeds in excess of 40mph.

These buggies can be made to handle really well at speed BUT you need to discard the stock wide front tyres, in fact all the stock wheels/tyres and use modern 2.2 inch buggy wheels/tyres with narrow fronts. The steering link and camber link lengths in the manual are wrong and lead to the car wondering about at speed (my daughters brand new Terra Scorcher suffered same issue, we adjusted the lengths to match mine and all is well now), these buggies will track arrow straight over rough tarmac/concrete at 30mph no issues at all once properly setup and using different oils and damper valves. I also use a very good quality Novak Rooster ESC which gives excellent braking and gives you confidence to push them hard.  One of the finest 4WD buggies that Tamiya sold in the 80's and yet so sadly overlooked by too many people.

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On 10/7/2020 at 8:12 PM, mud4fun said:

The steering link and camber link lengths in the manual are wrong and lead to the car wondering about at speed

Would you mind me asking what length you set them to please? I'd like it to be much less skittish than it is now. I've read your thread about the Vanquish/Avante/Egress and had seen that you'd said before how stable your daughters TS is.

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1 hour ago, EvilSpike said:

Would you mind me asking what length you set them to please? I'd like it to be much less skittish than it is now. I've read your thread about the Vanquish/Avante/Egress and had seen that you'd said before how stable your daughters TS is.

Yes, all our thundershot chassis cars (inc terra scorcher) are set with the following:

  • 13.5mm on the arm between servo and steering pivot (manual says 14mm)
  • 17.1mm on the two steering arms (manual says 18mm)
  • All use 2.2 inch wheels and tyres
  • Wide rears and narrow fronts for generally better handling
  • All rod ends have been replaced with new and balls greased
  • All run fully ballraced using quality bearings
  • Virtually zero slack in C hubs, uprights and upper camber links

We have been out this afternoon for a couple of hours racing and bashing. Did some more GPS testing too and I can assure you that all three thundershots tested, ran flat out down a 150 foot long straight bit of tarmac with zero steering correction needed and ran in an arrow straight line.

 

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I've got some new 2.2" wheels and tyres for it, I've gone for JC Racing Pepperpots and schumacher mini spike 2's with inserts like you linked to in the other thread.

Essentially from your measurements (thank you very much for those), you run the TS with a lot more toe out than the manual suggests. Have you played with the camber by altering the top arm lengths at all?

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On 10/16/2020 at 10:16 PM, EvilSpike said:

I've got some new 2.2" wheels and tyres for it, I've gone for JC Racing Pepperpots and schumacher mini spike 2's with inserts like you linked to in the other thread.

Essentially from your measurements (thank you very much for those), you run the TS with a lot more toe out than the manual suggests. Have you played with the camber by altering the top arm lengths at all?

Yes, we adjust camber depending on the track. In the last few weeks I've been running alot more camber on my buggies as it does reduce the grip rolling issue on tarmac, especially combined with lowering the car. For off road dirt tracks on soft surfaces I don't run much camber at all. 

On my thundershot I have just built a second set of shocks with spacers in them, bespoke lengths and firmer springs. When fitted to my thundershot it lowers it significantly, only 12mm clearance under front diff and 15-18mm under the rear. This works really well for tarmac racing, almost entirely eliminated grip rolls, instead back end slides nicely instead. For off road use I have kept the original yellow shocks and can swap those back on in 10 minutes. My thundershot was the fastest of all our buggies on the latest postal racing round 3 track, significantly faster than my Avante2001.

I also tried swapping to tarmac tyres but that didn't work so well, oddly enough super soft compound carpet tyres worked the best, amazing grip BUT they wear out very, very fast. At least the blue compound mini pins work on all surfaces and even on tarmac they last a good few races. My daughters have done about 2 hours hard racing on their mini pins on tarmac and they still have a few more races left in them. They barely wear at all when running on grass and dirt.

EDIT: I think the manual setup is for more toe-in, I run with pretty much zero toe-in as I find it suits the car better. That may be because we all run narrow front tyres but not sure, I seem to remember having to do the same change on my thundershots even back in the 90's when I was using the original tyres.

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Thank you very much for your advice sir :)

After taking it for a spin up and down the drive this morning in the damp (big skids on the wet tarmac!) I decided I had better clean and dry it off then change the tie rod lengths to Mr 4fun's suggested lengths. As soon as I started drying the chassis I could see what was obviously wrong, the steering horn had come a bit lose from the servo. Yeah, that'll do it... So I removed the bumper, popped the steering arm off the servo connection rod then out came the ESC and Servo. I tightened the servo bolt up as much as I could with a dab of threadlock, but even still there was some rotational play between the servo and the output arm in the three bits of Tamiya plastic. No matter how stiff the linkages are and how well the rest of the chassis is adjusted, I'll always have a five or ten degrees of steering slop when using that three part steering horn.

I could wedge a bit of plastic into the inner cup, but instead I had a nose on fleabay and found a couple of Chinese vendors offering alu steering arms for relatively pennies. I know they'll take between a week and two months to arrive, but for less than two quid each I thought they'd be worth a punt.

s-l500.jpg

And

s-l1600.jpg

Hopefully my 2.2" tyres will turn up in the next couple of days and I can mount them to the pepperpots.

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Thank you.

Sorry to hear that you have more issue :(

The only problem with the alloy servo arms is that they do not provide any servo saver action in the event of a crash, so the impact will go straight into the servo gears and damage the servo. 

The slack in the servo will be the C shaped disposable ring that sits between a base plate and the servo horn. They eventually get loose with age. Just need to buy a new one and it will remove alot of slack. They should be quite a tight fit onto the base plate, the gap in the C shaped ring should be narrower than the square lug on the baseplate so you have to push quite hard to fit the ring and it will stretch open the gap slightly. In the event of a collision the ring will open up even further and absorb most of the impact force, thus protecting the servo. Sadly after a big collision it should be replaced as they stretch and become loose.

I had exact same issue with my vanquish last week, knackered servo saver ring. I replaced with new and it removed a fair amount of slack in steering. However it is just part of the issue. Might as well check and renew the rod ends if they are worn too, even 0.25mm slop in each rod end soon adds up to considerable play in steering. Add that to incorrect geometry and the whole car is horrible to drive and yet it is a simple and quite cheap job to get near perfect :-)

 

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Thing is, it's an almost brand new car, I can't really have used it for more than a couple of hours all up since buying it in May? It's never been raced, just taken out about a dozen times either in front of the house where we live now, the carpark of the flat we were temporarily in over lockdown whilst waiting to move in here and twice to the old astroturf pitch in town. It's not been jumped at a skate or bmx track and hasn't really had any cartwheeling accidents.

I can certainly understand why you'd want a weak or sacrificial link between the wheels and servo, but the Tamiya one seems for too flexible for the purpose. I'll run with the alu arm when they arrive and if I find I trash a servo in short order then I'll go back to the plastic, three piece setup and just accept that it'll have some play in it.

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um, seems odd in that case then , they are normally quiet stiff when new, I'm only just starting to need to replace some of ours after 8-10 years of use. Some have even gone 20 years. 

There is almost zero play in any of the servo savers on our thundershots or even my daughters new Terra Scorcher.

Did you check that the baseplate is the correct one for your servo make? eg. futuba servo requires a futaba base plate? I ask because in some case the wrong baseplates will fit if pushed down hard but won't actually have the splines correctly engaged on the servo so will have play in them? may be worth double checking.

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I have just checked all our thundershots and terra scorchers, there is approx 3-4mm of sideways movement (slack) of the tyre before it starts to engage the servo. That is fine.  I have buggies with far more and that is normal. Once under power the tyres pull themselves straight anyway. It shouldn't cause you any noticeable issues in handling or steering.

I have the 3 piece servo savers on just about all my cars including Avante class buggies that run upto 35-40mph, never had a problem (other than natural wear). It sounds like you have either a faulty part or an incorrect part? The ring should be so stiff when new that it would require quite some force to make it open up. If it is opening up with no force at all then it is either broken or incorrect? Not sure how though as they only supply one ring in the kit (part P4). What make of servo is it?

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I'm 99% certain I've got the correct steering parts to fit the MG996R Servo that I've got in there. The inner plate slides on with little resistance but has no rotational slop. The slop comes from the middle C piece. As a halfway measure I could put a small tie wrap around the part to reduce that amount it can spread. We'll see on how much time I get in the next few days and how long it takes for the new arms to arrive.

As a random experiment today, because the car mainly runs on tarmac out the front of the house and I'm semi housebound a the moment (two fractures in the scapula and bruised hip due to a mountain bike crash) I decided to take the centre propshaft out and see what it was like in RWD. I'm hesitant to report it was actually quite a lot of fun! It's on road wheels at the mo, and so long as you're gentle with your inputs even at full speed it's stable, will understeer and then gently oversteer and it's often catchable too. Over the cut grass you have to knock off the power a bit or else it'll swap ends, and when coming back onto the tarmac it'll try doing it too.

So yeah, I enjoyed that! Another benefit it had was that I was using full throttle less, I had to build up to that, and so I had to wait less time for the ESC to cool down. I usually have to pause the fun to go and make a cup of tea once or twice as the ESC overheats and the car shuts off. When it did overheat this time I removed the inner dust-cover/driver and drove around until the battery ran flat. In 4WD it just understeers everywhere and as soon as you reduce the throttle it just points where you want it to; power to the front wheels can get you out of trouble every time. In 2WD it's much more of a challenge when just bashing about on your own. I won't leave it like this, but it is fun!

When that new servo arm arrives I'll redo the electrics and try and put the ESC further aft in the chassis then cut a small vent in the dust-cover to give it some airflow. I might try and use some filter material to stop too much dirt getting in. I'm only running a Sport Tuned motor and the TBLE-02s with a 7.2v NiCad . Right now the ESC is mounted on the servo as directed to in the instruction, but I have had it mounted further aft on the bulkhead before. When I take the R-clip off the main body I can feel the heat coming out of the cooling fins sometimes, there's no airflow up there at all really.

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@EvilSpike sorry, keep missing your replies :( If you want somebody to get a notification of your reply you can either quote them or use the @ symbol in front of their username, that way they'll get a notification of your reply. :)

Yeah we have have run our thundershots in 2WD in the past, I even ran one with a 9.6v battery in 2WD, that was hysterical :D (could only go in straight lines....)

None of our thundershot based cars are fitted with the tub covers or drivers, mainly because it causes the ESC's to overheat or simply limit space for laying out the electrics. If you are mainly running on tarmac then cover is not really needed.

We used to suffer understeer until fitting the narrow front wheels with better modern front tyres.

Our thundershots/terra scorchers now have excellent turn in, if you back off just before a corner (from a higher speed) the nose dives and the fronts grip tight and allow you to turn in tighter. My daughter has this technique down to a fine art and did an amazing number of laps on the postal race round 3 track using that very technique - managing to turn very tightly on the tight twisty track. She was running on tarmac using blue compound mini pin spikes. I only just beat her despite using tarmac or carpet tyres and having a much quicker and specially lowered car. I struggled to turn in as well as her.

I have modified my thundershot to allow a big LiPo to fit. That gives me 20-30 mins race time off a charge and is so much lighter that the buggy is even quicker, although it took a while to get used to the different handling characteristics.

This is my thundershot chassis, running bespoke shorter shocks to lower the buggy for tarmac racing, big LiPo and tarmac/carpet tyres. The carpet tyres grip well but the rear venom tarmac tyres are useless, mainly because they are too wide now for such a light buggy, they tend to lose traction to easily BUT they are fun because you can do donuts,  power slides  and drifts etc :D

There is alot of scope for tweaking these thundershot based chassis to suit different terrains and having even more fun!

tarmac_tyres.jpg

 

Only do this for tarmac racing, no good for off road, but by putting spacers on the shocks I lowered it enough to give a much lower CoG which significantly reduces grip rolling on tarmac.

 

844068335_ts_low(2).thumb.jpg.446731d5aa102050315d54e280aa8e87.jpg

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Thanks for the replies!

2 hours ago, mud4fun said:

None of our thundershot based cars are fitted with the tub covers or drivers, mainly because it causes the ESC's to overheat...

Ah, I wondered if it was just me but I guess not. It seemed to overheat less when I had the ESC mounted vertically in the middle bulkhead, I'll put it back there next time I open it up for the servo arm. I am still waiting for my friend to paint the drivers head, he's astoundingly good with the airbrushes, not so great at remembering to get around to unimportant stuff...

 

2 hours ago, mud4fun said:

if you back off just before a corner (from a higher speed) the nose dives and the fronts grip tight and allow you to turn in tighter.

That's exactly what I found too, knock off 25% throttle, give it a quarter of a second then turn and it's really compliant. I use the CVA's it came with and have the largest preload spacers on the rear shocks, the thinnest in the front and it's lovely and direct. I'd love to find somewhere to race it one day, I'm between Truro and Falmouth and the only club near me races GT12's indoors during the winter or big things like Associated B6.1's over jumps that would kill my car. Ah well, it's fun here anyway.

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56 minutes ago, EvilSpike said:

I'd love to find somewhere to race it one day, 

I'm not sure if you have entered the postal racing series yet?

That is an excellent way of 'racing' with others even if you are on your own with no track nearby. As long as you can find a large flat area of grass or tarmac near you bug enough to setup the course as defined by TurnipJF at the start of each round then you can take part. It is great fun, it allows you to practise your racing skills and car setup skills etc. My daughters and I have been taking part and are really enjoying it. We are not pro racers, I used to race 30+ years ago but nothing since other than bashing and racing against my daughters on our garden track. So this postal racing challenge has been enormous fun and has really improved our driving skills. 

We are currently in the middle of round 3, entries close midnight this coming sunday, round 3 track is quite small and is devilishly tricky to get good times on but is only 5m x 4m so even allowing yourself a couple of metres all around you should be able to find a car park or lawn big enough?

see halfway down page 11 for round 3 track plan video.

The rules are pretty simple:

  • Setup the track as per TurnipJF's instructions (he normally posts a video explaining the track layout at the start of each round)
  • From a standing start drive the track until a 5 min countdown has completed
  • finish the lap you were on after the 5 mins was up
  • submit the number of laps you managed to TurnipJF via private message (to keep the results secret until results day) plus the make/model of car, its motor/battery spec and the surface type (eg. grass, tarmac) and whether it was dry or wet.

 

 

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